Epidermal growth factor, α-transforming growth factor and breast cancer
Evidence exists that epidermal growth factor (EGF) and alpha transforming growth factor (αTGF) are important in breast cancer. An inverse relationship between epidermal growth factor receptor (EGF-R) and oestrogen receptor (ER) has been reported by some, (1) but not all workers (2). The aim in this thesis was to develop assays to measure, levels of EGF, and determine EGF-R status in human breast tumours. These results were then correlated with each other, with ER and node status and histological grade (Bloom & Richardson). An additional aim in this thesis was to develop a source of αTGF in conditioned median (CM) from a transformed cell line. After extraction and purification, the αTGF was intended for use as an immunogen to produce a polyclonal antiserum which could be used in either an RIA or ELISA. EGF was measured by a radioimmunoassay (RIA) utilising a rabbit antimouse EGF antiserum. This assay (sensitivity 0.1ng/ml) was demonstrated to have no cross reactivity with αTGF. The EGF-R assay was similar to that described by Sainsbury. (1) In a series of 88 human breast tumours 47 (53.4%) were found to contain extractable EGF. Forty eight (54.5%) were EGF-R positive and 39 (44.3%) were ER positive. A direct relationship between EGF and ER+ ve status was found (p < 0.01). Significantly higher levels of EGF were extracted from ER+ ve tumours (p = 0.049) compared with that from ER-ve tumours. However no relationship between EGF-R and EGF or ER status was found, or between EGF levels and histological grade or node status. A suitable cell line which produced αTGF, was obtained and culture conditions optimised. Alpha-TGF was assayed by a radioreceptor assay which utilised a cell line rich in EGF-R (A431). Extraction of αTGF was based on the principles of molecular grading by gel filtration (Sephadex G50), and ion exchange (Sephadex CM C25). By this process the αTGF was purified and separated it from any EGF present. By this method 20μg of αTGF was produced from 61t of CM. 1) Sainsbury JRC, Farndon JR, Serbet GV, Harris AL. Epidermal-growth-factor-receptors and oestrogen receptors in human breast cancer. Lancet 1985; 1: 364-368. 2) Fitzpatrick SL, Brightwell J, Wattliff JL, Barrows GH, Schultz GS. Epidermal growth factor binding by breast tumour biopsies and relationship to oestrogen receptor and progestin receptor levels. Cancer Res 1984; 44: 3448-3453.